Effect of inhibition of Na +K + ATpase on the prostacyclin generation of cultured human vascular endothelial cells

Abstract

Prostacyclin (PGI 2) generation of cultured human vascular endothelial cells (VEC) was observed coincidentally with the increase of 45Ca net influx. Ca ionophore A23187 enhanced not only PGI 2 generation and 45Ca net influx but also 45Ca efflux. PGI 2 generation was completely abolished by the pretreatment with Ca ++ immobilizer, TMB-8. A Na + ATPase inhibitor, ouabain increased 45Ca net influx, but decreased 45Ca efflux, and enhanced PGI 2 generation. These observation indicate that PGI 2 generation of VEC may be regulated by not only Ca ++ but also Na +, and it was suggested that enhanced PGI 2 generation by ouabain might be derived from the increased cytosolic Ca ++ concentration by the decreased Ca ++ efflux, and it was considered to be originated from the suppression of Na +Ca ++ exchange systems by the increased intracellular Na + concentration via inhibition of Na +K + ATPase activity by ouabain. Enhancement of PGI 2 generation of VEC by the increased ouabain like substances (OLS) in hypertension is suspected to be beneficial on the maintenance of vascular homeostasis.